/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.metadata.mtree.store.disk;

import org.apache.iotdb.db.metadata.mnode.IMNode;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

public class CachedMNodeContainer implements ICachedMNodeContainer {

    private long segmentAddress = -1;

    private Map<String, IMNode> childCache = null;
    private Map<String, IMNode> newChildBuffer = null;
    private Map<String, IMNode> updatedChildBuffer = null;

    @Override
    public int size() {
        return getSize(childCache) + getSize(newChildBuffer) + getSize(updatedChildBuffer);
    }

    private int getSize(Map<String, IMNode> map) {
        return map == null ? 0 : map.size();
    }

    @Override
    public boolean isEmpty() {
        return isEmpty(childCache) && isEmpty(newChildBuffer) && isEmpty(updatedChildBuffer);
    }

    private boolean isEmpty(Map<String, IMNode> map) {
        return map == null || map.isEmpty();
    }

    @Override
    public boolean containsKey(Object key) {
        return containsKey(childCache, key)
                || containsKey(newChildBuffer, key)
                || containsKey(updatedChildBuffer, key);
    }

    private boolean containsKey(Map<String, IMNode> map, Object key) {
        return map != null && map.containsKey(key);
    }

    @Override
    public boolean containsValue(Object value) {
        return containsValue(childCache, value)
                || containsValue(newChildBuffer, value)
                || containsValue(updatedChildBuffer, value);
    }

    private boolean containsValue(Map<String, IMNode> map, Object value) {
        return map != null && map.containsValue(value);
    }

    @Override
    public IMNode get(Object key) {
        IMNode result = get(childCache, key);
        if (result != null) {
            return result;
        }
        result = get(newChildBuffer, key);
        if (result != null) {
            return result;
        }
        return get(updatedChildBuffer, key);
    }

    private IMNode get(Map<String, IMNode> map, Object key) {
        return map == null ? null : map.get(key);
    }

    @Nullable
    @Override
    public synchronized IMNode put(String key, IMNode value) {
        if (newChildBuffer == null) {
            newChildBuffer = new ConcurrentHashMap<>();
        }
        return newChildBuffer.put(key, value);
    }

    @Nullable
    @Override
    public synchronized IMNode putIfAbsent(String key, IMNode value) {

        IMNode node = get(key);
        if (node == null) {
            if (newChildBuffer == null) {
                newChildBuffer = new ConcurrentHashMap<>();
            }
            node = newChildBuffer.put(key, value);
        }

        return node;
    }

    @Override
    public synchronized IMNode remove(Object key) {
        IMNode result = remove(childCache, key);
        if (result == null) {
            result = remove(newChildBuffer, key);
        }
        if (result == null) {
            result = remove(updatedChildBuffer, key);
        }
        return result;
    }

    private IMNode remove(Map<String, IMNode> map, Object key) {
        return map == null ? null : map.remove(key);
    }

    @Override
    public synchronized void putAll(@Nonnull Map<? extends String, ? extends IMNode> m) {
        if (newChildBuffer == null) {
            newChildBuffer = new ConcurrentHashMap<>();
        }
        newChildBuffer.putAll(m);
    }

    @Override
    public synchronized void clear() {
        childCache = null;
        newChildBuffer = null;
        updatedChildBuffer = null;
    }

    @Nonnull
    @Override
    public Set<String> keySet() {
        Set<String> result = new TreeSet<>();
        result.addAll(keySet(childCache));
        result.addAll(keySet(newChildBuffer));
        result.addAll(keySet(updatedChildBuffer));
        return result;
    }

    private Set<String> keySet(Map<String, IMNode> map) {
        return map == null ? Collections.emptySet() : map.keySet();
    }

    @Nonnull
    @Override
    public Collection<IMNode> values() {
        Collection<IMNode> result = new ArrayList<>();
        result.addAll(getValues(childCache));
        result.addAll(getValues(newChildBuffer));
        result.addAll(getValues(updatedChildBuffer));
        return result;
    }

    private Collection<IMNode> getValues(Map<String, IMNode> map) {
        return map == null ? Collections.emptyList() : map.values();
    }

    @Nonnull
    @Override
    public Set<Entry<String, IMNode>> entrySet() {
        Set<Entry<String, IMNode>> result = new HashSet<>();
        result.addAll(entrySet(childCache));
        result.addAll(entrySet(newChildBuffer));
        result.addAll(entrySet(updatedChildBuffer));
        return result;
    }

    private Set<Entry<String, IMNode>> entrySet(Map<String, IMNode> map) {
        return map == null ? Collections.emptySet() : map.entrySet();
    }

    @Nullable
    @Override
    public synchronized IMNode replace(String key, IMNode value) {
        IMNode replacedOne = replace(childCache, key, value);
        if (replacedOne == null) {
            replacedOne = replace(newChildBuffer, key, value);
        }
        if (replacedOne == null) {
            replacedOne = replace(updatedChildBuffer, key, value);
        }
        return replacedOne;
    }

    private IMNode replace(Map<String, IMNode> map, String key, IMNode value) {
        return map == null ? null : map.replace(key, value);
    }

    @Override
    public long getSegmentAddress() {
        return segmentAddress;
    }

    @Override
    public void setSegmentAddress(long segmentAddress) {
        this.segmentAddress = segmentAddress;
    }

    @Override
    public boolean isVolatile() {
        return segmentAddress == -1;
    }

    @Override
    public boolean isFull() {
        return true;
    }

    @Override
    public boolean isExpelled() {
        return !isVolatile()
                && isEmpty(childCache)
                && isEmpty(newChildBuffer)
                && isEmpty(updatedChildBuffer);
    }

    @Override
    public boolean hasChildInNewChildBuffer(String name) {
        return containsKey(newChildBuffer, name);
    }

    @Override
    public boolean hasChildInBuffer(String name) {
        return containsKey(updatedChildBuffer, name) || containsKey(newChildBuffer, name);
    }

    @Override
    public Iterator<IMNode> getChildrenIterator() {
        return new CachedMNodeContainerIterator();
    }

    @Override
    public Iterator<IMNode> getChildrenBufferIterator() {
        return new BufferIterator();
    }

    @Override
    public Iterator<IMNode> getNewChildBufferIterator() {
        return getNewChildBuffer().values().iterator();
    }

    @Override
    public Map<String, IMNode> getChildCache() {
        return childCache == null ? Collections.emptyMap() : childCache;
    }

    @Override
    public Map<String, IMNode> getNewChildBuffer() {
        return newChildBuffer == null ? Collections.emptyMap() : newChildBuffer;
    }

    @Override
    public Map<String, IMNode> getUpdatedChildBuffer() {
        return updatedChildBuffer == null ? Collections.emptyMap() : updatedChildBuffer;
    }

    @Override
    public synchronized void loadChildrenFromDisk(Map<String, IMNode> children) {
        if (childCache == null) {
            childCache = new ConcurrentHashMap<>();
        }
        childCache.putAll(children);
    }

    @Override
    public synchronized void addChildToCache(IMNode node) {
        String name = node.getName();
        if (containsKey(name)) {
            return;
        }
        if (childCache == null) {
            childCache = new ConcurrentHashMap<>();
        }
        childCache.put(name, node);
    }

    @Override
    public synchronized void appendMNode(IMNode node) {
        if (newChildBuffer == null) {
            newChildBuffer = new ConcurrentHashMap<>();
        }
        newChildBuffer.put(node.getName(), node);
    }

    @Override
    public synchronized void updateMNode(String name) {
        IMNode node = remove(childCache, name);
        if (node != null) {
            if (updatedChildBuffer == null) {
                updatedChildBuffer = new ConcurrentHashMap<>();
            }
            updatedChildBuffer.put(name, node);
        }
    }

    @Override
    public synchronized void moveMNodeToCache(String name) {
        IMNode node = remove(newChildBuffer, name);
        if (node == null) {
            node = remove(updatedChildBuffer, name);
        }
        if (childCache == null) {
            childCache = new ConcurrentHashMap<>();
        }
        childCache.put(name, node);
    }

    @Override
    public synchronized void evictMNode(String name) {
        remove(childCache, name);
    }

    public synchronized String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append("CachedMNodeContainer:{");
        builder.append("childCache:[");
        for (IMNode node : getValues(childCache)) {
            builder.append(node.getName()).append(",");
        }
        builder.append("];");
        builder.append("newChildBuffer:[");
        for (IMNode node : getValues(newChildBuffer)) {
            builder.append(node.getName()).append(",");
        }
        builder.append("];");
        builder.append("updateChildBuffer:[");
        for (IMNode node : getValues(updatedChildBuffer)) {
            builder.append(node.getName()).append(",");
        }
        builder.append("];");
        builder.append("}");
        return builder.toString();
    }

    private class CachedMNodeContainerIterator implements Iterator<IMNode> {

        Iterator<IMNode> iterator;
        byte status = 0;

        CachedMNodeContainerIterator() {
            iterator = getChildCache().values().iterator();
        }

        @Override
        public boolean hasNext() {
            if (iterator.hasNext()) {
                return true;
            }
            while (!iterator.hasNext()) {
                if (!changeStatus()) {
                    return false;
                }
            }
            return true;
        }

        @Override
        public IMNode next() {
            return iterator.next();
        }

        private boolean changeStatus() {
            switch (status) {
                case 0:
                    iterator = getNewChildBuffer().values().iterator();
                    status = 1;
                    return true;
                case 1:
                    iterator = getUpdatedChildBuffer().values().iterator();
                    status = 2;
                    return true;
                default:
                    return false;
            }
        }
    }

    private class BufferIterator implements Iterator<IMNode> {
        Iterator<IMNode> iterator;
        Iterator<IMNode> newBufferIterator;
        Iterator<IMNode> updateBufferIterator;
        byte status = 0;

        BufferIterator() {
            newBufferIterator = getNewChildBuffer().values().iterator();
            updateBufferIterator = getUpdatedChildBuffer().values().iterator();
            iterator = newBufferIterator;
        }

        @Override
        public boolean hasNext() {
            if (iterator.hasNext()) {
                return true;
            }
            while (!iterator.hasNext()) {
                if (!changeStatus()) {
                    return false;
                }
            }
            return true;
        }

        @Override
        public IMNode next() {
            return iterator.next();
        }

        private boolean changeStatus() {
            if (status == 0) {
                iterator = updateBufferIterator;
                status = 1;
                return true;
            }
            return false;
        }
    }
}
